Nonlinear Analysis of Pfr – Separation – Recycle Systems Coupling Exothermic and Endothermic Reactions

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Steady-state behaviour of PFR-separation-recycle systems with simultaneous exothermic and endothermic, first-order reactions

A systematic investigation of plug-flow reactor (PFR)-separation-recycle systems where first-order exothermic and endothermic reactions are simultaneously performed is presented. The nonlinear behaviour is analyzed for two flowsheet alternatives and four plantwide control structures. It is shown that the system can exhibit a complex nonlinear behaviour. For the parameter values used, regions of unfeasibility, two or three multiple steady states and branches of isolated solutions were found. The undesired nonlinear phenomena can be avoided by fixing the reactor-inlet flow rates of each reactant or, when this is impossible due to the flowsheet structure, by providing sufficient cooling capacity. © 2008 Elsevier Ltd. All rights reserved

A reduced model for the freezing step in ice cream manufacture

This contribution deals with the development of a reduced yet complex model, to support process design and operation. The model is computationally effective. The main physical phenomena considered in the model are the axial convective transport of mass, the radial outflow of heat at coolant wall to the refrigerant, the growth of the frozen ice layer, the periodic removal of the ice crystals by scraping and the melting of the ice crystal population in the bulk liquid. Rate equations for the relevant physical phenomena, as well as phase equilibrium conditions and thermodynamic equations of state are also present. The target output variables to meet the product quality specifications are the ice crystals size and the air content. Results of some preliminary steady state simulations are presented

An Analytical Study of Mass Transfer Efficiency in Double-Pass Parallel-Plate Mass Exchangers under Uniform Wall Fluxes

[[abstract]]A permeable barrier was inserted to divide an open duct into two subchannels of uniform wall fluxes for conducting double-pass laminar countercurrent operations. The mass transfer rate of such a double-pass device was substantially improved and has been investigated theoretically by using an eigenfunction expansion in power series. The theoretical predictions of mass-transfer efficiency enhancement in double-pass parallel-plate mass exchangers were represented graphically and compared with those in an open duct of single-pass operation (without a permeable barrier inserted). The results show that the double-pass operation can effectively enhance the mass transfer efficiency and especially when the permeable-barrier position is appropriately adjusted.[[notice]]補正完畢[[incitationindex]]SCI[[incitationindex]]E